JP2008032131A - Hydraulic auto tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the axial length of a hydraulic auto tensioner short and prevent a hydraulic oil from leaking out of a pressure chamber of the hydraulic auto tensioner. <P>SOLUTION: The inside of a cylinder 9 is divided by a rod 13 and a sleeve 12 into a pressure chamber 14 and a reservoir chamber 15. A leak gap 23 allowing the pressure chamber 14 to communicate with the reservoir chamber 15 is formed between the sliding surfaces of the rod 13 and the sleeve 12. A return spring 18 is installed to bias the rod 13 in the direction that increases the volume of the pressure chamber 14. An opening 24 allowing the pressure chamber 14 to communicate with the reservoir chamber 15 is formed in a flange part 11. A check valve 27 allowing only the flow of the hydraulic oil from the reservoir chamber side toward the pressure chamber side is installed in the opening 24. The check valve 27 is so disposed that it is overlapped with the rod 13 in a direction perpendicular to its axis. The surface of the cylinder 9 facing the pressure chamber 14 is covered by a steel bottomed sleeve 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydraulic auto tensioner used for maintaining tension of a belt that drives an auxiliary machine such as an alternator.

  An auxiliary machine of an automobile, for example, an alternator, a car air conditioner, a water pump, or the like has a rotating shaft connected to a crankshaft of an engine by a belt, and is driven by the engine through the belt. In order to keep the tension of this belt within an appropriate range, generally, a pulley arm that is swingable about a fulcrum shaft, a tension pulley that is rotatably attached to the pulley arm, and a direction in which the tension pulley is pressed against the belt. A tension adjusting device including a hydraulic auto tensioner that urges a pulley arm is used.

  As a hydraulic auto tensioner incorporated in this tension adjustment device, a sleeve is inserted into a bottomed cylinder, and a plunger is slidably inserted in the axial direction into the sleeve to partition the cylinder into a pressure chamber and a reservoir chamber. Further, it is known that the plunger is provided with a rod that moves integrally with the plunger, and a return spring that biases the rod in the direction in which the volume of the pressure chamber increases (Patent Documents 1 and 2). In this hydraulic auto tensioner, when the rod moves to a position where the urging force of the return spring balances with the belt tension, the tension of the belt is absorbed and the belt tension is kept within an appropriate range.

  A leak gap is formed between the sliding surfaces of the plunger and the sleeve so that the pressure chamber communicates with the reservoir chamber. When the rod moves in a direction in which the volume of the pressure chamber is reduced, the hydraulic oil in the pressure chamber has a leak gap. Flows through to the reservoir chamber. At this time, since the flow rate of the hydraulic oil flowing through the leak gap is limited, the rod moves slowly, and the belt tension is kept stable.

The plunger has a through hole that connects the pressure chamber and the reservoir chamber, and the opening on the pressure chamber side of the through hole allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side. When the valve is provided and the rod moves in the direction in which the volume of the pressure chamber increases, the hydraulic oil flows from the reservoir chamber side to the pressure chamber side through the check valve. Therefore, the rod quickly moves in the direction in which the volume of the pressure chamber expands, and absorbs the slack of the belt quickly.
JP-A-10-19099 JP-A-10-306860

  However, in this hydraulic auto tensioner, since the plunger and the check valve are arranged side by side in the axial direction, the axial length is long and it is difficult to install in a narrow space.

  Therefore, the inventor of the present invention stores hydraulic oil in a bottomed cylinder and shortens the axial length of the hydraulic auto tensioner by providing a sleeve having an outward flange portion in the cylinder. A rod is inserted into the sleeve so as to be slidable in the axial direction, and the cylinder is divided into a pressure chamber and a reservoir chamber by the rod and the sleeve, and the pressure is slid between the sliding surface of the rod and the sleeve. A throttle passage for communicating the chamber and the reservoir chamber, a return spring for urging the rod in the direction of enlarging the volume of the pressure chamber is provided, and an opening for communicating the pressure chamber and the reservoir chamber in the flange portion A check valve that allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side is provided at the opening, and the check valve is perpendicular to the rod. Arranged to overlap in the hydraulic auto-tensioner has devised.

  In this hydraulic auto tensioner, the check valve is arranged so that it overlaps the axis perpendicular to the rod, so the check valve and the rod are perpendicular to the axis than when the check valve is arranged axially to the rod. The length in the axial direction can be kept short because it overlaps, and it is easy to install in a narrow space.

  However, in this hydraulic auto tensioner, if the pressure in the pressure chamber is directly received by the inner surface of the cylinder, the cylinder may be damaged. In particular, when the cylinder is made of an aluminum alloy, the yield strength of the cylinder is insufficient, and there is a high possibility that the cylinder will be damaged by the pressure in the pressure chamber. Further, when the cylinder is formed by die casting, it has been necessary to impregnate the cylinder in order to prevent hydraulic oil from leaking.

  The problem to be solved by the present invention is to keep the length of the hydraulic auto tensioner in the axial direction short and to prevent leakage of hydraulic oil from the pressure chamber of the hydraulic auto tensioner.

  In order to solve the above-described problems, the above-described configuration is employed in a hydraulic auto tensioner, and the surface of the cylinder facing the pressure chamber is covered with a bottomed sleeve made of steel.

  The check valve of the hydraulic auto tensioner includes, for example, a ring-shaped valve body that is detachably provided on the pressure chamber side surface of the flange portion, and a valve spring that urges the valve body toward the flange portion. And can be configured.

  In the hydraulic auto tensioner according to the present invention, the inner surface of the cylinder receives the pressure of the pressure chamber via the steel bottomed sleeve, so that the cylinder is not easily damaged and the hydraulic oil is less likely to leak.

  1 and 2 show a tension adjusting device for a belt 1 for driving an automobile auxiliary machine. This tension adjusting device has a tension pulley 2 that contacts the belt 1 and a pulley arm 3 that rotatably supports the tension pulley 2, and the pulley arm 3 is attached to a fulcrum shaft 5 that is fixed to the engine block 4 shown in FIG. It is supported so that it can swing.

  One end of an auto tensioner 6 according to an embodiment of the present invention is rotatably connected to the pulley arm 3 around a connecting shaft 7, and the other end of the auto tensioner 6 is rotatable to a connecting shaft 8 fixed to the engine block 4. It is connected to. The auto tensioner 6 biases the pulley arm 3 to press the tension pulley 2 against the belt 1.

  As shown in FIG. 2, the hydraulic auto tensioner 6 has a bottomed cylinder 9 made of an aluminum alloy, and hydraulic oil is stored in the cylinder 9. In the cylinder 9, a bottomed sleeve 10 made of steel and a sleeve 12 having an outward flange portion 11 at the lower end are provided. The flange portion 11 is placed on the upper end of the bottomed sleeve 10. ing. A rod 13 is inserted into the sleeve 12 so as to be slidable in the axial direction, and the inside of the cylinder 9 is partitioned into a pressure chamber 14 and a reservoir chamber 15 by the rod 13 and the sleeve 12. The bottomed sleeve 10 covers the surface of the cylinder 9 that faces the pressure chamber 14.

  A connecting piece 16 connected to the pulley arm 3 is fixed to the upper end of the rod 13. A return spring 18 is incorporated between the connecting piece 16 and the flange portion 11 via a spring seat 17 fitted to the outer periphery of the rod 13, and the return spring 18 extends the rod 13 in the direction of expanding the volume of the pressure chamber 14. Energized.

  The spring seat 17 is provided with a cylindrical skirt portion 19 that faces the outer periphery of the cylinder 9. An O-ring 20 that contacts the inner periphery of the skirt portion 19 is provided on the outer periphery of the upper portion of the cylinder 9, and this O-ring 20 prevents foreign matter from entering the cylinder 9.

  A protrusion 21 is formed on the outer periphery of the cylinder 9 below the O-ring 20, and the inner periphery of the skirt portion 19 is locked below the contact position with the O-ring 20 and protrudes toward the inner diameter side. A nail 22 is formed. The protrusion 21 locks the locking claw 22 and prevents the skirt portion 19 from coming off the cylinder 9.

  As shown in FIG. 3, a leak gap 23 is formed between the sliding surfaces of the rod 13 and the sleeve 12 to allow the pressure chamber 14 and the reservoir chamber 15 to communicate with each other. The leak gap 23 is very small and restricts the flow rate of the hydraulic oil flowing from the pressure chamber 14 to the reservoir chamber 15.

  In the flange portion 11 of the sleeve 12, openings 24 for communicating the pressure chamber 14 and the reservoir chamber 15 are formed at intervals in the circumferential direction as shown in FIG. As shown in FIG. 3, the opening 24 is provided with a ring-shaped valve body 25 slidably provided on the surface of the flange portion 11 on the pressure chamber 14 side, and the valve body 25 is biased toward the flange portion 11. A check valve 27 including a valve spring 26 is provided. The check valve 27 allows the flow of hydraulic oil from the reservoir chamber 15 side to the pressure chamber 14 side, but prohibits the flow of hydraulic oil from the pressure chamber 14 side to the reservoir chamber 15 side.

  The check valve 27 is configured such that the inner diameter of the valve body 25 is larger than the outer diameter of the rod 13 and does not overlap the rod 13 when viewed in the axial direction. The valve spring 26 includes a cylindrical portion 28 that is press-fitted into the inner periphery of the bottomed sleeve 10, and a claw portion 29 that is bent toward the inner diameter side along the lower end of the cylindrical portion 28. A plurality are formed at regular intervals in the direction.

  Further, as shown by a two-dot chain line in FIG. 3, the check valve 27 overlaps the rod 13 in a direction perpendicular to the axis in a state where the rod 13 is at the stroke end on the side of reducing the volume of the pressure chamber 14. Has been placed.

  Next, an operation example of the hydraulic auto tensioner 6 will be described.

  When the tension of the belt 1 increases, the tension is transmitted to the rod 13 through the pulley arm 3 and the connecting piece 16 in order, and the pressure in the pressure chamber 14 is increased. When the pressure in the pressure chamber 14 becomes higher than the pressure in the reservoir chamber 15, the hydraulic oil in the pressure chamber 14 flows into the reservoir chamber 15 through the leak gap 23 as shown in FIG. 3. At this time, since the check valve 27 is closed, the hydraulic oil does not flow through the opening 24 of the flange portion 11. Thus, the hydraulic oil flows through the leak gap 23, so that the rod 13 moves, and the tension pulley 2 moves to a position where the tension of the belt 1 and the urging force of the return spring 18 are balanced. At this time, since the flow rate of the hydraulic oil flowing through the leak gap 23 is limited, the tension pulley 2 moves slowly and absorbs the tension while keeping the belt 1 in a stable state.

  On the other hand, when the tension of the belt 1 decreases, the pressure in the pressure chamber 14 decreases due to the urging force of the return spring 18. When the pressure in the pressure chamber 14 becomes lower than the pressure in the reservoir chamber 15, the check valve 27 is opened. As shown in FIG. 5, the hydraulic oil in the reservoir chamber 15 passes through the opening 24 of the flange portion 11 and enters the pressure chamber 14. Flowing. The rod 13 is moved by the flow of the hydraulic oil, and the tension pulley 2 is moved to a position where the tension of the belt 1 and the urging force of the return spring 18 are balanced. At this time, the tension pulley 2 moves quickly and absorbs the slack of the belt 1 quickly.

  In this hydraulic auto tensioner 6, the check valve 27 is disposed so as to overlap the rod 13 in a direction perpendicular to the axis in a state where the rod 13 is at the stroke end on the side of reducing the volume of the pressure chamber 14. Compared with the rods arranged side by side in the axial direction, the check valve 27 and the rod 13 overlap each other in the direction perpendicular to the axis, so that the length in the axial direction can be reduced, and it is easy to install in a narrow space.

  Further, in this hydraulic auto tensioner 6, since the inner surface of the cylinder 9 receives the pressure of the pressure chamber 14 via the bottomed sleeve 10 made of steel, when the belt tension becomes excessive and the pressure in the pressure chamber rises. In addition, the cylinder 9 is not easily damaged. Further, even when the cylinder 9 is formed by die casting of an aluminum alloy, the inner surface of the cylinder 9 receives the pressure of the pressure chamber 14 through the bottomed sleeve 10 made of steel. Therefore, it is not necessary to impregnate the cylinder 9 with resin or the like, which is economical.

  Further, in the hydraulic auto tensioner 6, the rod 13 is guided by the sleeve 12 and positioned at the center of the cylinder 9, so that the wear ring that supports the rod 13 so as to be slidable and prevents the rod 13 from falling down is used as the cylinder. It is economical because it is not necessary to incorporate it in the board.

  Further, since the hydraulic auto tensioner 6 is provided with the check valve 27 in the opening 24 of the flange portion 11, it is not necessary to form a passage in which the check valve 27 is provided in the rod 13. Therefore, an extruded product or a die-cast product can be used as it is as the rod 13 without being processed, which is economical.

  In the above embodiment, the check valve 27 is disposed so as to overlap the rod 13 in the direction perpendicular to the axis only when the rod 13 is at the stroke end on the side of reducing the volume of the pressure chamber 14. 27, the rod 13 always overlaps the rod 13 in the direction perpendicular to the axis in the process from the stroke end on the side where the volume of the pressure chamber 14 is reduced to the stroke end on the side where the volume of the pressure chamber 14 is increased. You may arrange in. In short, it is only necessary that the check valve overlaps the rod in the direction perpendicular to the axis in a state where the rod is at the stroke end on the side of reducing the volume of the pressure chamber.

  In the above embodiment, the urging force of the valve spring 26 acts on the valve body 25 more uniformly by urging the valve body 25 with the claw portions 29 arranged at regular intervals in the circumferential direction. However, other types of valve springs may be used. For example, a coil spring is incorporated between the pressure chamber 14 side surface of the valve body 25 and the bottom surface of the cylinder 9, and the valve spring is used as the valve spring. The body 25 may be biased toward the flange portion 11.

The front view which shows the tension adjustment apparatus incorporating the hydraulic type auto tensioner of embodiment of this invention Sectional view along the line II-II in FIG. Fig. 2 is an enlarged cross-sectional view of the hydraulic auto tensioner near the check valve. Sectional view along line IV-IV in FIG. FIG. 3 is an enlarged cross-sectional view showing a process in which the rod of FIG. 3 moves in the direction of enlarging the volume of the pressure chamber.

Explanation of symbols

9 Cylinder 10 Bottomed sleeve 11 Flange portion 12 Sleeve 13 Rod 14 Pressure chamber 15 Reservoir chamber 18 Return spring 23 Leak gap 24 Opening 25 Valve element 26 Valve spring 27 Check valve

Claims (2)

  A hydraulic oil is stored in a bottomed cylinder (9), a sleeve (12) having an outward flange portion (11) is provided in the cylinder (9), and a rod (13) is provided in the sleeve (12). The rod (13) and the sleeve (12) divide the cylinder (9) into a pressure chamber (14) and a reservoir chamber (15), and the rod (13) And a throttle passage (23) for communicating the pressure chamber (14) and the reservoir chamber (15) between the sliding surfaces of the sleeve (12) and increasing the volume of the pressure chamber (14). A return spring (18) for urging the rod (13) is provided, and an opening (24) for communicating the pressure chamber (14) and the reservoir chamber (15) is formed in the flange portion (11). (24), reservoir chamber (15) A check valve (27) that allows only the flow of hydraulic oil from the pressure chamber (14) to the pressure chamber (14) side, and the check valve (27) is arranged so as to overlap the rod (13) in the direction perpendicular to the axis, A hydraulic auto tensioner in which a surface of the cylinder (9) facing the pressure chamber (14) is covered with a bottomed sleeve (10) made of steel.   A ring-shaped valve body (25) in which the check valve (27) is detachably provided on the pressure chamber (14) side surface of the flange section (11), and the valve body (25) is connected to the flange section. The hydraulic auto tensioner according to claim 1, comprising a valve spring (26) biased toward (11).

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